2019-07-09 P&E Agenda - Item 10 - Attachment 1 - Coastal Hazards Risk, Vulnerability and Adaptation Assessment

Noosa Shire Council Coastal Hazard Mapping                                                               14
Erosion Prone Area Assessment




          Figure 3-2   Conceptual Illustration of the Open Coast Calculated Erosion Distance Formula



3.3      Planning Period (N)
         The present-day, 2040, 2070 and 2100 planning horizons have been assessed. For each
         timeframe, it has been assumed that the storm erosion component (C1 + C2), the rate of long term
         erosion (R) and the dune slumping component (D) remains consistent. For example, the short term
         erosion associated with a storm event is the same for all planning horizons.

         The erosion due to an increase to mean sea level (S) for each timeframe is ultimately based on a
         SLR projection of 0.8 m by 2100, as adopted by the Queensland Government for land use planning
         purposes. SLR benchmarks for the intervening planning horizons have been determined from
         projections that are consistent with the current literature. This has been previously summarised as
         part of the CHAP Scoping Study (BMT WBM 2017).

3.4      Rate of Long Term Erosion (R)
         The rate of long term erosion can be estimated by extrapolating past trends from analysis of
         historical survey data and/or determining any deficit in the local sediment budget, typically via a
         combination of data analysis and longshore sediment transport modelling. In instances when there
         is insufficient data is available to accurately assess (R) on an individual beach basis, the
         component is simply accounted for by adopting an allowance of 10 m (the minimum allowance for
         N x R required by DEHP 2013).

         Changes to the beach profile in response to wave events can be clearly detected in the historical
         survey datasets, with volumetric changes of ±30,000 m3/year common at Noosa Main Beach (e.g.



G:\Admin\B22613.g.mpb.Noosa_CHAS\R.B22613.002.04.NSC_CHAP_Mapping.docx